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What is a placenta? What does the placenta consist of?

Site of contact between embryonic and maternal tissues to allow exchange of material between the two.

Maternal endometrium, extra-embryonic fetal membranes: allantois, chorion, amnion, (yolk sac is a transient placenta in early species)


What is the conceptus?


What has to happen after fertilization of the ovum?

* development within zona pellucida

* hatching of the blastocyst from the zona pellucida

* maternal recognition of pregnancy

* formation of extraembryonic membranes


What is the clinical significance of the chorioamniotic raphe/ mesamnion in a cow? What is different in a horse?

If a cow gives birth, the cervix will open, chorionallantois will rupture, amnion also has to rupture since it is attached tot he chorionallantois. What lubricates the calf? Amniotic fluid (not as watery as in a horse)

* in horses- one big allantois sac, foetus floating around in the amnion. Amnion is not attached. So in horses, you will see the water break- this is when the chorion is breaking. You will see the amnion first which is around the foal (whitish, bluish)... danger the foal has that calf doesn't have-- if the amnion doesn't rupture, suffocation can occur, this doesn't really happen to calves because of the chorionamniotic raphe (membrane facilitates birth, vs. amnionic fluid)


What is meant by blastulation?



What marks the end of dioestrus? What has to happen to prevent luteolysis during pregnancy?

Marked by the regression of the CL. Maternal recognition of pregnancy


What is the placenta made up of?

Maternal uterine tissue + fetal extraembryonic membranes


What are the placental functions?

* In all species: exchange of gas and nutrients between dam and fetus, fetal waste removal

* vital endocrine organ

* in some species itis the sole source for pregnancy maintaining progestagens in late gestation


What happens if you get luteolysis during pregnancy?



What do all domestic mammals have in terms of placentas?

Chorioallantoic placenta (usually fused)


What are the barriers separating maternal from fetal circulations?

Epitheliochorial- horses, cows and pigs (ruminants are often now classified as synepithelial chorial)

Endotheliochorial- dogs and cats

Hemochorial- primates and rodents


What is the barrier separating maternal circulation from fetal circulation in ruminants?

Areas where the maternal epithelium is altered- binucleate and trinucleate


What needs to be bigger, the more layers exist between the maternal and fetal circulation?

Bigger surface area

(epitheliochorial (most surface area)--> synepitheliochorial--> endothelialchorial--> haematochorial)


What are the 3 possible configurations of chorionic attachment?


Deciduate vs. non-deciduate

What about ruminants?

How much maternal tissue is lost with it, what stays behind?

** ruminants the "black sheep"-  partial deciduate (some say non-deciduate)


How long after parturition can you breed a horse? How long for a dog?

10 days (horse)

2 months (dog)

**what is needed to get the endometrium normal again, related to how much damaged occurred


Placentation- Ruminant

clear bubble around embryo- amnion (amnionic fluid is what fetus floats in)

* necrotic tip- get it in pigs as well- at some point the growth is so extreme the tissue outgrows the blood supply-- not a problem-- it is sterile

(conceptus is on the opposite end of the nectrotic tip, really long in the picture)

** the tiny little heart supports the entire conceptus and foetal membranes


Who is this from? What are caruncles?


* caruncles - predetermined site of the placental attachment.


What are cotyledon? What is the placentome?



When does the cotyledonary attachment to caruncles of uterus initiated? What is prior? When is attachment well established?



What is the maternal and fetal circulation separated by in ruminants?



What occurs with bovine placentogenesis?



When does the allantois begin to form?



What is the urachus?

Kind of the like the urethra in the foetus. From apex of the bladder to umbilical cord, where it runs parallel to the blood vessels and empties into the allantois.


Horse placentation



No caruncles in horses- but if you look at it microscopically- looks like tiny placetomes one next to each other.

** at day 35 sinus terminalis- where the umbilicus attaches, where the yolk sac was or is at that stage. Chorionic girdle- invasive trophoblast cells in a circle.




Why do you want more follicles? Progesterone, maintains pregnancy




When does amniogenesis occur in horses? Allantois?


equine umbilical cord at term


Distended Urachus- (intra-amnionic) (twisted- with haemorrhage- a twist is not a huge concern, but seeing any pathology in the cord like haemorrhage is a concern)


Amnion- (chorion and allantois are still inside the mare)


sometimes called allantoic calculi




In a pig, when are the first chorionic folds? When is apposition to endometrium well established (epitheliochorial)?

** some of the fetal membranes actually fuse together which means sometimes quite a few piglets are born before you see any membranes





PLacentation- carnivore?


What is the zonary placenta in a carnivore?


WHat kind of organization in the chorionic villi?


What is the marginal hematoma?


What are the main differences of placentation of different species?


Why is it important to expel the placenta?


Origin of the cotyledone? Origin of caruncle?

Cotyledone- fetal chorion

Caruncle- mother's endometrial lining of the uterus


What is the main goal to maintain pregnancy?

Maintain adequate levels of progestagens to maintain pregnancy to term


What is the main source of progesterone in equine pregnancy until day 40?


What happens for the first 3 weeks with the endometrial cups in a horse?


The production of what is closely related to the weight of the endometrial cups?



What does ecG do?


What are the ways that progesterone is maintained in a horse throughout pregnancy?


When pregnancy is terminated whether induced or natural, greater than x days may not result in return to estrus? What may dely return to regular cycle for 3 to 4 months?

>34- to 37 days

* Persistence of endometrial cups may delay return to regular cycles for 3 to 4 months (the cups continue to function & produce eCG; they survive until the time of thei normal demise)


What happens with relaxin during an equine pregnancy?

* relaxin promotes uterine and cervical growth and remodeling that is essential for normal fetal growth and parturition. Relaxin decreases collagen content in the extracellular matrices of the pubic symphysis and cervix, inhibits uterine contractility, and plays a role in mammary gland development. (angiogenic and vasodilatory effects on endometrial and mammary tissues)

* maternal concentration of relaxin begins to increase after day 75 of gestation and peaks at day 175 and then remains elevated until foaling, followed by precipitous decline postpartum

* low maternal concentrations of relaxin during late gestation have been associated with high-risk pregnancies and complicated deliveries.


What happens with progesterone in queens, bitches, and sows?


What happens with progesterone in cows, mares, and ewes (humans)?


What do goats rely on solely for their progesterone?

Ovulatory CLs for their whole gestation- meaning you can give prostaglandin for termination


What is hcG? What does it do?

Human chorionic gonadotropin is produced by trophoblast cells of humans non-human primates. Luteotropic effect on the ovulatory corpus luteum. It binds to luteal LH receptors and if given to non-pregnant females in the late follicular phase it can induce ovulation


How do humans mantain high progesterone?

Initially from luteotropic effect of hcG. At about 2.5-3 months of gestation the placenta produces the majority of the progesterone and continues this role until parturition.


What does placental lactogen do?

* produced by binucleate giant cells that are of trophoblastic origin and invade the endometrium.-- hypothesized that the sire has an effect on the degree to which the fetus can produce placental lactogen- therefore, it might be possible for the sire to influence milk production of the dam (sire-on-fetus-hypothesis)

Believed to act as a GH, stimulating growth of the fetus (somatotropic). It also has a growth promoting effect on the mammary gland (lactogenic). The degree to which placental lactogen is lactogenic or somatotropic depends on the species.

In the ewe and the woman the lactogenic effect of placental lactogen is more pronounced than the somatotropic effect that is not the case in the cow and the goat, where both effects are comparable.


WHat happens with oestrogen in different species?

In most species it increases at the end of gestation (progesteragens are converted to oestrogens). Only in women oestrogen is high throughout the pregnancy and also the mare has significant amounts throughout the second half of gestation.


At 2 weeks, what are these?

Why are they two different sizes?

What if they were not completely separated?

Concepti in a horse-- twins. (this is past half blastocyst stage)

** Why one is smaller than another: may not have ovulated exactly at the same time- may have 2 days in between OR could be a sign one of them is not doing so well and is on the way out

** important to consider- is it a cyst? Ideally, you have done an ultrasound before breeding 



Other than pregnancy, what else could enlarge the uterus?

Pyometra, Hydrometra


What imagine modality would you choose to check if they are alive or dead?

Ultrasound, cannot tell with radiography


Why is ultrasound preferred with pregnancy?

* more portable, earlier confirmation of pregnancy, determination of foetal viability, estimation of foetal age, +/- foetal sexing (large animals), can tell if foetus is alive, enlarges to develop head and tail pole, limb buds, heart beat, skeleton, and other internal organs


When is ultrasound reliable in the bitch and queen?

from day 28 post LH peak (day 23-25 you should be able to make out a visible heart beat)

* can be performed from day 20 in bitch and day 14 in queen

* count number of gestational sacs from 25-35 days


How can you age the fetus using ultrasound?

By measuring the gestational sac diameter


What are the other options if no ultrasound is available (e.g. need specific lighting, not too much direct light on the machine)?

Manual pregnancy (palpation) and hormonal/biochemical assays


Problems with ultrasound and palpation?


* e.g. problem with manual count of puppies


When can you sex a fetus in a mare?

* day 60-70. Looking for the genital tubercle to work out whether it is a penis or a clitoris


How do you age a bovine fetus?

* foetal size (or head thorax size at 9+ weeks), presence of amniotic vesicle (6-11 weeks), differentiation of foetus (can you see head, limbs, ribs), presence and size of cotyledons, nature of fluid (black vs. cloudy)


What is the optimal temperature for analyzing sperm? And optimal conditions?

37 C

* they don't like light

* the longer you look at them, the worse they look (deteriorate in a few minutes)


What is a hemocytometer?

Determine the concentration of sperm (or cells)


Semen sample characteristics

* motility: actively moving forward across the stage

* no WBCs

* volume

* density

* wave motion

* % alive

* head and tail morphology

*cells other than spermatozoa

* concentration

(not abnormal to have 20% with coiled tails or any other abnormalities)



What is live/dead stain aka morphology stain for sperm?

Red sperm are dead sperm- but difficult to do properly- so more important to use it to look at morphology

* in order to get a more acurate result you need to keep them at optimal temperature (37 C)


Which is foetus and which is embryo?

Bottom- foetus because you can identify species and maybe gender


Which species does the CL have a finite life span?

Dogs & cats- only a few days short of a normal full term pregnancy- so even if a virus has killed everything on board, the CL stays active- you think the animal is still pregnant with live on board



What causes luteolysis? What is the source?

Prostaglandin, uterus (endometrium)


What cells of the placenta produce progesterone in cows, ovine, and mares in the second half (approx) of pregnancy?

chorion cells of the placenta


Outermost aspect- chorionic aspect of the chorionallantois from a foal (directly interdigitating with Mom's endometrium). The white area is around the base of the pregnant horn is the remnants (starting day 35) chorionic trophoblasts left the fetal membrane and tunneled into Mom's endometrial stroma and set up endometrial cups-- once they are set up--> source of pregnant mare serum gonadotrophin--> pumping out progesterone-- set up additional CL--- important source of boosting progesterone to maintain pregnancy. Up to 140 days where you'd expect to still have endometrial cups producing progesterone. If you have one fetus on board and it dies during the period where endometrial cups are there-- then externally you will still think it is still a live pregnant, but PSEUDOPREGNANT-- won't see expulsion until the cups have reached the end of their lifespan.



Early embryonic mortality- broad term for loss of conceptus in the early stage of in utero life. Death of zygote before it is implanted all the way to death of embryo.

* the window where most pregnancies are lost, up to 30% of all pregnancies are lost at this stage

* caused by genetic abnormalities, meiosis is complicated so things going wrong with the gametes, chromosomal numerical abnormalities (age of gametes linked), structural problems with the gametes exposure to toxins, drugs, viruses, venereal infections


Cause EEM

Protozoa, Tritrichomonas fetus, Campylobacter fetus, Mycoplasma




Uterus, could cause abortion, what is it?



Uterus, could cause abortion, what is it?



Placental mole- rarely, following the death of an embryo, the extra-embryonic placental membranes may persist and continue to grow to form a cystic placental mole. May undergo necrosis and be discharged, some become invasice and burrow into the uterus and even penetrate to reach the peritoneal surface (more common in humans)


What are the possibilities with foetal death and disease?

Abortion, maceration, mummification, stillbirth


Abortion vs. Stillbirth

Stillbirth- term foetus- dead on arrival but at the stage where it should be capable of surviving independently

* abortion- way too early- not capable of surviving on its own


What starts delivery?

The fetus is releasing ACTH --> fetal cortisol surge


fetus retained, cervix is closed - no bacteria otherwise maceration (progesterone source retained), simply dessication- gradually dehydrating

e.g. porcine parvovirus- the most common cause in piglets all around the world, toxoplasma, Neosporum caninum, BVDV, twinning in foals (1% of pregnancies)



* decomposition (softening, lysis, and liquefaction) of the foetus and its membranes due to the action of bacteria products and/or proteolytic products of leukocytes

* endometritis, pyometera, metritis-- high risk for mom: septicaemia, toxaemia... could perforate uterus because bones are left behind


What happens to gestation?

Prolongation- due to prosencephalic and hence hypothalamic and/or neurohypophyseal malformation


What damage can infectious agents cause to a pregnant animal? What are the important ones in cattle in Australia?

Affect the placenta, foetus, mom

* Campylobacter fetus subsp. venerealis, C. fetus subsp. fetus, Neospora caninum


Cow fetal membrane with cotyledons-- placentitis (oedema, calcification)


C. burnetii affecting a fetal placenta of a cow-- lesions concentrated in the cotyledons because it is haematogenous